1. Field of the Invention
The present invention generally relates to pressing devices, and more particularly, to a pressing device for latching and releasing a chucking device which is used for holding a cutting tool.
2. Discussion of the Related Art
A cutting tool, for example a milling cutter, is generally used in a machining process for machining a mold or any other workpieces. Before the machining process, the cutting tool should be mounted in a chucking device. The chucking device together with the cutting tool is then mounted in a machine tool.
A typical chucking device generally includes a collet and a collet holder. The principle of the chucking device is disclosed in U.S. Pat. No. 6,908,085. The chucking device is suitable for tools, in particular cutting tools. A cylindrical bore defined in the collet serves to accommodate the shank of the tool. A plurality of radially directed slots is defined in a sidewall of the collet for increasing radial elasticity of the collet. A tapered recess is defined in the collet holder for receiving the collet. The taper angle of the tapered recess is smaller than the self-locking angle. When the collet with inserted tool is pressed into the tapered recess of the collet holder, there is a radial pressure, by means of which the tool is securely held. Since the taper angle is smaller than the self-locking angle, the collet, once it has been pressed in, no longer has to be additionally fastened in the collet holder.
The collet is generally pressed to move into or out of the tapered recess of the collet holder by a pressing device so as to be latched to or be released from the collet holder. The pressing device includes a first movable member and a second movable member, a driving structure for driving the first movable member to move. Each of the first and second movable members includes an upper clamping element and a lower clamping element. Each of the upper clamping elements of the first and second movable members defines a first latching groove. The first latching grooves of the upper clamping elements of the first and second movable members cooperatively form a first clamping hole for clamping the collet. The first clamping hole has a size corresponding to that of the collet. Similarly, each of the lower clamping elements of the first and second movable members defines a second latching groove. The second latching grooves of the lower clamping elements of the first and second movable members cooperatively form a second clamping hole for clamping the collet holder. The second clamping hole has a size corresponding to that of the collet holder.
To use the pressing device, the first and second movable member are disposed in the driving structure, and the first and second movable member separate from each other. The collet of the chucking device is partly received in the first latching groove of the first movable member or in the first latching groove of the second movable member. The collet holder of the chucking device is partly received in the second latching groove of the first movable member or in the second latching groove of the second movable member. The first and second movable members abut each other, thereby forming the first clamping hole for clamping the collet and the second clamping hole for clamping the collet holder. The upper clamping elements are driven by the driving structure to move together with the collet towards the lower clamping elements so that the collet is inserted into the collet holder. Thus, the collet together with the inserted cutting tool is latched in the collet. If the collet with the inserted cutting tool is to be released from the collet, the upper clamping elements are driven to move together with the collet away from the lower clamping elements. Thus, the collet with the inserted cutting tool is pulled out of the collet holder.
The sizes of the first and second latching grooves of the first and second movable members of the pressing device are determined by the size of the collet and the collet holder of the chucking device. If a size of the tool is changed, the chucking device must be changed accordingly. Therefore, different tools need different chucking devices to be mounted and different chucking devices need different latching grooves of movable members of the pressing device. However, the pressing device described above is only suitable for one kind of tool and the corresponding chucking device for the tool. If a different tool needs to be mounted in the chucking device, the first and second movable members of the pressing device are generally replaced by the appropriate first and second movable members, in order to define corresponding latching grooves. Having to frequently change the first and second movable members for a different tool costs time and a service life of the pressing device will be reduced. The typical pressing device is not convenient to be used for assembling tools having different sizes to the corresponding chucking devices.
Therefore, a new pressing device is desired in order to overcome the above-described shortcomings.